Ankle-foot orthosis

ABSTRACT

One embodiment provides an ankle-foot orthosis ( 32 ) for resisting plantarflexion of a patient&#39;s foot, the orthosis ( 32 ) comprising: a resiliently flexible sock-like structure ( 34 ) enveloping, in use, at least a portion of a patient&#39;s lower leg in the vicinity of the ankle and at least a portion of the plantar ( 46 ) and dorsal ( 48 ) aspects of the patient&#39;s foot. Another embodiment provides an ankle-foot orthosis ( 1 ) for resisting plantarflexion of a patient&#39;s foot, the orthosis ( 1 ) comprising: a resilient rib ( 3 ) locatable, in use, along and in abutment with at least a portion of the dorsal aspect of the patient&#39;s foot and at least a portion of the patient&#39;s lower leg, the orthosis ( 1 ) comprising means ( 7 ) for securing the rib ( 3 ) to the patient&#39;s foot and lower leg.

[0001] This invention relates to ankle-foot orthosis.

[0002] Orthoses are mechanical devices which impose forces upon a limbof a patient and can be used for a variety of different purposes. Forexample, orthosis may be provided for supportive, functional, correctiveor protective purposes, or for a combination of these. Ankle-footorthosis are typically provided to provide protection to the ankle andfoot of a patient as well as to provide support against excessiveplantarflexion or dropping of the foot. In addition to this resistivefunction, they may also be employed to assist dorsiflexion of thepatient's foot during the push off phase of the patient's gait.

[0003] Foot plantarflexion is a medical condition that can arise from avariety of causes, for example disease or congenital abnormality.Patients affected by this condition typically experience difficulty inwalking as they must lift their foot excessively from the ground inorder to avoid stumbling.

[0004] A variety of different ankle-foot orthosis have previously beenproposed for resisting plantarflexion, and in some cases foradditionally assisting dorsiflexion. FIGS. 1a, 1 b, 2 a and 2 billustrate two of these previously proposed devices.

[0005]FIG. 1a illustrates one previously proposed ankle-foot orthosisbefore it is assembled on a patient. The orthosis 10 must be used inconjunction with a shoe 12 that provides close contact between the shoeand the foot in the region of the instep. The orthosis 10 comprises apair of supporting metal uprights 14, one connected to either side ofthe shoe 12 in the region of the heel 16. The connections each comprisea plantarflexion stop 18 that resists foot drop and may also includesprings (not shown) to assist dorsiflexion. The upper ends of theuprights are connected to a supporting strap 20 which is securable aboutthe patient's calf. With reference to FIG. 1b, it can be seen that thesupporting strap 20 provides support about the patient's calf, and thatthe plantarflexion stops 18 and shoe 12 provide support under the footof the patient to resist plantarflexion.

[0006]FIGS. 2a and 2 b illustrate another previously proposed orthosisdevice which must also be used in conjunction with a shoe that providesclose contact between the shoe and the foot in the region of the instep.In this example, the orthosis 22 comprises a one-piece plastics moulding24 which comprises a calf abutting region 26 and a sole abutting region28. The top of the calf abutting region 26 is provided with a closuremechanism 27 that enables the device to be secured to the calf of apatient. The sole abutting region 28 acts in conjunction with the shoe30 to support the foot of the patient. The stiffness of the plasticsmoulding and the shape thereof in the region of the ankle defines theamount of resistance to plantarflexion. If more resistance is required,then the gap across the front of the ankle can be reduced, or thestiffness of the plastics can be increased.

[0007] Both of the aforementioned previously proposed devices adequatelysupport the foot of a patient to resist plantarflexion. However, theyboth exhibit serious deficiencies that make them highly unpopular withpatients.

[0008] A first disadvantage is that both of the previously proposedorthosis are large bulky devices which are clearly visible when worn.Thus, the patient's illness or abnormality is immediately apparent toothers and this can adversely affect the patient's state of mind. Thisproblem can be particularly apparent with child patients as the orthosisis an immediately obvious difference which other children can ridicule.It can also be a serious problem for adult patients as a visible deviceimmediately labels them as a disabled or abnormal person withcorresponding ramifications for their personal and working lives.

[0009] A further disadvantage is that both of these previously proposeddevices must be worn with shoes. Thus, if a patient wished to walkwithout shoes or to go swimming, for example, then they would have to doso without any means for resisting plantarflexion.

[0010] A further disadvantage is that these previously proposed devicescan cause extreme discomfort when worn. This problem is particularlyapparent with the orthosis of FIGS. 2a and 2 b as the device extendsunder the foot of the patient and thus the full weight of the patientbears upon the device when the patient walks.

[0011] Yet another disadvantage is that both of these previouslyproposed devices are difficult and time consuming to put on and takeoff. Furthermore, the second device often requires the fabrication ofspecial shoes as it is often not possible to fit the device withinnormal off-the-shelf shoes. Finally, both devices are expensive to makeand fit as they must be closely fitted to the feet and legs of thepatient, and as they are made from relatively expensive materials.

[0012] U.S. Pat. No. 4,559,934 discloses an orthosis comprising asupport stocking with a pair of reinforced portions to which a pocket isattached. A support device is secured between the pockets and tensioningstrap is provided by means of which the tension in the support devicemay be increased or decreased as desired.

[0013] U.S. Pat. No. 5,676,641 discloses an ankle support particularlydesigned to restrain the ankle from rolling to the inside or outside.The support comprises a support sock over which various straps arewound.

[0014] U.S. Pat. No. 4,651,723 discloses a leather attachment securableabout the lower leg of a patient. The attachment is connected to a platespring that may be located within the shoe of a wearer to resistplantarflexion of the patient's foot.

[0015] It is an object of aspects of the invention to alleviate some orall of these disadvantages.

[0016] In accordance with the invention, there is provided an ankle-footorthosis comprising: a resiliently flexible sock-like structureenveloping, in use, at least a portion of a patient's lower leg in thevicinity of the ankle and at least a portion of the plantar and dorsalaspects of a patient's foot, characterised in that said sock-likestructure is of silicone and in that said orthosis provides, in use, apredetermined substantially constant resistance to planterflexion of thepatient's foot.

[0017] Thus, this aspect of the invention provides a discretearrangement which adequately resists plantarflexion without requiringthe patient to wear a shoe.

[0018] Preferably the orthosis comprises a reinforcing means for furtherresisting planterflexion of the foot. The reinforcing means may be alength of tape, the ends of the tape being joined together to form afigure-of-eight passing under the instep, behind the ankle and crossingon the dorsal aspect of the foot. Alternatively, the reinforcing meansmay comprises a rib running along at least a portion of the dorsalaspect of the foot and substantially midway between the medial malleolusand the lateral malleolus. Preferably the reinforcing means has agreater resilience than the sock-like structure.

[0019] Preferably, the orthosis comprises an insertion slit extendingmidway between the medial malleolus and the lateral malleolus towardsthe calcaneum, means being provided to securely close the slit once thepatient's foot has been inserted in the orthosis.

[0020] The closing means may comprise a mechanical hook and loopfastener, a set of hoops or hooks being provided adjacent one edge ofthe slit and a corresponding set of hooks or hoops being provided on aclosure member affixed to the other side of the slit, respective hooksand loops being connectable to securely close the slit. Alternatively,the closing means may comprise a zip fastener secured to opposite sidesof the slit. As a further alternative, the closing means may comprise aset of eyelets closable by a lace.

[0021] Preferably, the orthosis envelops the dorsal and plantar aspectsof the foot without enveloping the toes. Preferably, the orthosisenvelops the plantar aspect of the foot without enveloping thecalcaneum. The orthosis could envelop the calcaneum if, for example,mechanical correction of the heel bone is required. The device may alsobe contoured on the surface abutting, in use, the plantar aspect of thefoot to aid support of the metatarsals and to position the footcorrectly.

[0022] Preferably, the sock-like structure is a 35 shore siliconeelastomer, or a higher or lower shore silicone elastomer. Preferably,the reinforcing means is of silicone.

[0023] Preferably, the orthosis is skin coloured and/or fabricated byinjection moulding. The orthosis could alternatively be brightlycoloured so as to appeal to children.

[0024] In accordance with a second aspect of the invention, there isprovided a kit comprising a plurality of orthosis as described herein,the orthosis being of varying size and shape for fitting to feet ofdifferent sizes and shapes. The kit may also comprise differentlycoloured orthosis to allow the matching of the colour of the orthosis tothe skin colour of the patient.

[0025] In any event, it is preferred that the rib is of plastics, suchas polypropylene or ortholene.

[0026] Preferably, the orthosis is skin coloured and/or fabricated byinjection moulding. The orthosis could be formed by stamping from sheetmaterial. The orthosis could be brightly coloured so as to appeal tochildren.

[0027] In accordance with another aspect of the invention, there isprovided a kit comprising a plurality of orthosis as described herein,the orthosis being of varying size and shape for fitting to feet ofdifferent sizes and shapes. The kit may also comprise differentlycoloured orthosis to allow the matching of the colour of the orthosis tothe skin colour of the patient.

[0028] Embodiments of the present invention will now be described, byway of example only, with reference to the accompanying drawings, inwhich:

[0029]FIGS. 1a and 1 b are schematic representations of one previouslyproposed orthosis;

[0030]FIGS. 2a and 2 b are schematic representations of anotherpreviously proposed orthosis;

[0031]FIG. 3 is a schematic representation of an orthosis according to afirst aspect of the invention; and

[0032]FIG. 4 is a schematic representation of an orthosis according to asecond aspect of the invention.

[0033]FIG. 5 is a schematic representation of another orthosis;

[0034]FIG. 6 is a side view of the orthosis of FIG. 5; and

[0035]FIG. 7 is a schematic representation of yet another orthosisaccording to a fourth aspect of the invention.

[0036] With reference to FIG. 3, the orthosis 32 comprises a resilientlyflexible sock-like structure 34 and a reinforcing means 36 (shown inghost), which in this embodiment is a tape 38 - the ends of which arejoined together to form a figure-of-eight which passes under the instep,behind the ankle and crosses on the dorsal aspect of the foot. Thereinforcing means may be formed integrally with the sock-like structureor, alternatively, the reinforcing means may be formed separately andsubsequently inserted within the sock-like structure.

[0037] The resilience of the sock-like structure and the reinforcingmeans are chosen, and may be varied, in dependence upon the degree towhich the patient suffers from plantarflexion. Indeed, the reinforcingmeans 36 can be dispensed with if sufficient resistance toplantarflexion is provided by the sock-like structure 34. It ispreferred for the resilience of the reinforcing means 36, if provided,to be greater than that of the sock-like structure 34.

[0038] In this embodiment, the orthosis 32 envelops a portion of thepatients lower leg which preferably includes the medial malleolus 40(the inside of the ankle) and the lateral malleolus 42 (the outside ofthe ankle), the calcaneum 44 (the heel), a portion of the plantar aspect46 of the foot (the sole of the foot) and a portion of the dorsal aspect48 of the foot (the back of the foot). In this embodiment, the toes 49of the foot are not enveloped by the orthosis, although they could beenveloped if desired. It is preferred that the orthosis extends beyondthe medial and lateral malleoli.

[0039] The sock-like structure 34 is provided with a slit (not shown)which extends in a direction towards the calcaneum between the medialand lateral malleoli. In this embodiment, the slit is closable by amechanical hook and loop fastener 50, such as velcro®. One portion ofthe fastener (ie. either a hook portion or a loop portion) is affixed toone side of the slit. The other portion of the fastener 50 is affixed toa strap 52 that is affixed to the other side of the slit.

[0040]FIG. 4 shows a second embodiment of the invention wherein theorthosis 32 is provided with a zip fastener 54, respective parts ofwhich are secured to either side of the slit. In this embodiment, thesock-like structure 34 does not envelop the calcaneum 44 of the foot. Ithas been found that the orthosis 32 can be made significantly morecomfortable if both the calcaneum 44 and toes 49 are not enveloped bythe sock-like structure 34. In this embodiment, the reinforcing meanscomprises a rib 56 which extends partway along the dorsal aspect of thefoot. The rib may be formed integrally with the orthosis. Alternatively,the rib may be removably insertable into a pocket provided on the dorsalaspect of the foot to allow for the stiffness of the rib, and/or theangle of support (by inserting differently shaped ribs), to be changedif desired.

[0041] The orthosis of either embodiment may be coloured so that it canbe matched to the skin colour of the patient, and may be provided in avariety of different sizes and shapes. The orthosis is preferablymanufactured by injection moulding. Alternatively, the orthosis may bemanufactured by milling (as described below) and subsequently buildingup layers of the device upon a suitable cast.

[0042] The orthosis may be of a variety of different materials chosen tohave a suitable resilience. For example, the orthosis could be ofrubber, silicone, plastics or of any other material apparent to personsskilled in the art. Preferably the orthosis is of 35 shore siliconeelastomer. The orthosis may be of a greater or lesser shore valuedepending upon the particular needs of the patient to which it is to befitted. The reinforcing means may be of silicone, with a chosen shorevalue, or may be of any other material apparent to persons skilled inthe art. The reinforcing means could be of the same material as thesock-like structure, or could be of a different material. For example,in the arrangement of FIG. 4, the rib may be of a metal.

[0043] Two suitable elastomers are sold under the product names HCR9960and MED4035 by Nusil Technology of 1050 Cindy Lane, Carpinteria, Calif.,USA. HCR9960 has a working time of approximately 12 hours and MED4035has a shorter working time of approximately 3 to 4 hours, after whichthe elastomer cures. The elastomers are thermo-setting and are strainedthrough a 200 mesh screen to remove particulate contaminants.

[0044] The elastomers are supplied as A and B components which arepreferably combined in equal portions on a two roll mill, or othersuitable device, prior to use. A suggested sequence for blending the twocomponents is to first soften part B on the mill and then soften part A,after which an equal weight of part B should be added to part A and thenthoroughly mixed. At this stage, it is recommended to keep thetemperature of the material as low as possible so as to maximise thetable life of the elastomer. The mixture may then be manually fitted toa plaster cast of a patient's foot, or more preferably supplied toinjection moulding apparatus to mould a suitably shaped orthosis. Curingof the blended elastomer may be accelerated by heat and can take from 3to 4 hours. The cure may be inhibited by any ambient traces of organicrubbers and other substances and thus it is preferred for thefabrication of the orthosis to be conducted in a thoroughly cleanedarea.

[0045]FIG. 5 is a schematic representation of another orthosis 1 thatcomprises a resilient rib 3 that is locatable in use along the dorsalaspect of the patient's foot 5. As shown, the orthosis 1 extends fromapproximately the base of the patient's toes up to the lower portion ofthe patient's shin.

[0046] The rib 3 is formed of a material that is preferably relativelylight-weight and resilient—such as a plastic. A preferred material isortholene or polypropylene, but numerous other suitable materials (suchas a metal, an alloy or carbon fibre or similar material for example)will be apparent to persons skilled in the art. The orthosis could beinjection moulded, or for a more precise fit could be individuallyfitted to a patient's foot.

[0047] In order for the orthosis to benefit the patient, it must somehowbe secured to the patient's foot. In the embodiment of FIG. 5, theorthosis 1 is secured to the foot 5 by way of a pair of straps 7, whichin the preferred embodiment include mechanical hook-and-loop fasteners(not shown) such as velcro® that enable the straps 7 to be securedaround the patients foot and lower leg respectively. Alternativefastening mechanisms, such as pop fasteners, could be provided inaddition or instead of velcro®. When the straps are secured about thepatient's foot and lower leg, the orthosis 1 is secured to the patient'sfoot and plantarflexion is resisted. The arrangement of FIG. 5 isparticularly advantageous for use in warmer climates as the majority ofthe patient's foot is not covered by the orthosis 1.

[0048]FIG. 6 is a side view of the orthosis 1 of FIG. 5 illustrating thepoints at which pressure is applied to the patient's foot by the device.As shown, the orthosis 1 applies pressure to the patient's foot at threediscrete locations (i), (ii) and (iii). Application of pressure to thefoot at these three locations causes plantarflexion to be resistedwhilst also aiding dorsiflexion. In this way, the orthosis 1 aids thepatient during all stages of the walking motion. Furthermore, theorthosis 1 shown is considerably more comfortable for the patient towear than previously proposed devices as it does not extend beneath thefoot and thus the weight of the patient does not bear upon the orthosis1 during walking.

[0049] A further orthosis is shown in FIG. 7. This orthosis is primarilydesigned for use in conjunction with a shoe 9, and comprises an orthosis1 of polypropylene, for example, and a single strap 11 provided at theend of the reinforcing means closest to the patient's leg, in use.Securing the strap 11 around the patient's lower leg and inserting thefoot 5 and orthosis 1 within a shoe 9 provides an orthosis that iscapable of resisting plantarflexion of the patient's foot. As analternative to providing a strap, the upper end of the orthosis could beadhered to the patients lower leg.

[0050] If the straps of the orthosis of FIG. 5 are removably attached tothe rib 3, then the orthosis or FIG. 5 could be converted for use with ashoe, as shown in FIG. 7, simply by removing the lower strap.

[0051] As a further alternative that is not illustrated in the drawings,the straps could be dispensed with and the rib could then be adhered atleast at the ends thereof to the Patient's lower leg and foot. Theadhesive could be any adhesive suitable for bonding articles to skin.

[0052] The orthosis may be coloured so that it can be matched to theskin colour of the patient, and may be provided in a variety ofdifferent shapes and sizes.

[0053] The orthosis may be of a variety of different materials chosen tohave a suitable resilience. For example, the orthosis could be ofrubber, silicone, plastics, carbon fibre or of any other materialapparent to persons skilled in the art. In a preferred example, theorthosis is of 35 shore silicone elastomer. The orthosis may be of agreater or lesser shore value depending upon the particular needs of thepatient to which it is to be fitted.

[0054] It will be understood, of course, that the invention has beendescribed herein by way of example only and that modifications may bemade within the scope of the invention.

1. An ankle-foot orthosis (32) comprising: a resiliently flexiblesock-like structure (34) enveloping, in use, at least a portion of apatient's lower leg in the vicinity of the ankle and at least a portionof the plantar and dorsal aspects (46,48) of a patient's foot,characterised in that said sock-like structure (34) is of silicone andin that said orthosis provides, in use, a predetermined substantiallyconstant resistance to planterflexion of the patient's foot.
 2. Anorthosis according to claim 1, comprising a reinforcing means (38,56)for providing a further resistance to planterflexion of the patient'sfoot.
 3. An orthosis according to claim 2, wherein the reinforcing meanscomprises a length of tape (38), the ends of the tape being joinedtogether to form a figure-of-eight passing under the instep, behind theankle (40,42) and crossing on the dorsal aspect (48) of the foot.
 4. Anorthosis according to claim 2, wherein the reinforcing means comprises arib (56) running along at least a portion of the dorsal aspect (48) ofthe foot and substantially midway between the medial malleolus (40) andthe lateral malleolus (42).
 5. An orthosis according to claim 4, whereinthe rib (56) is of plastics.
 6. An orthosis according to claim 4,wherein the rib (56) is of silicone.
 7. An orthosis according to claim4, wherein the rib (56) is of polypropylene.
 8. An orthosis according toclaim 4, wherein the rib (56) is of ortholene.
 9. An orthosis accordingto claim 4, wherein the rib (56) is of carbon fibre.
 10. An orthosisaccording to any preceding claim, wherein the reinforcing means (38,56)has a greater resilience than the sock-like structure (34).
 11. Anorthosis according to any preceding claim, comprising an insertion slitextending substantially midway between the medial malleolus (40) and thelateral malleolus (42) at the back of the ankle towards the calcaneum,means (50,54) being provided to securely close the slit once thepatient's foot has been inserted in the orthosis.
 12. An orthosisaccording to claim 11, wherein the closing means comprises a mechanicalhook and loop fastener (50), a set of hoops or hooks being providedadjacent one edge of the slit and a corresponding set of hooks or hoopsbeing provided on a closure member affixed to the other side of theslit, respective hooks and loops being connectable to securely close theslit.
 13. An orthosis according to claim 1 1, wherein the closing meanscomprises a zip fastener (54) secured to opposite sides of the slit. 14.An orthosis according to claim 11, wherein the closing means comprises aset of eyelets provided on either side of the slit, the slit beingclosable by a lace fed through the eyelets.
 15. An orthosis according toany preceding claim, wherein the orthosis envelops at least a portion ofthe dorsal (48) and plantar (46) aspects of the foot without envelopingthe toes (49).
 16. An orthosis according to any preceding claim, whereinthe orthosis envelops at least a portion of the plantar aspect (46) ofthe foot without enveloping the calcaneum (44).
 17. An orthosisaccording to any preceding claim, wherein the sock-like structure is of35 shore silicone elastomer.
 18. An orthosis according to any precedingclaim, wherein the orthosis is skin coloured.
 19. An orthosis accordingto any preceding claim, wherein the orthosis is fabricated by injectionmoulding.
 20. An orthosis according to any of claims 1 to 18, whereinthe orthosis is stamped or pressed from sheet material.
 21. A kitcomprising a plurality of orthosis (32) according to any precedingclaim, the orthosis being of varying size and shape for fitting to feetof different sizes and shapes.
 22. A kit according to claim 21,comprising differently coloured orthosis to allow the matching of thecolour of the orthosis to the skin colour of the patient.